The present invention relates to a method and apparatus for providing optional service functions in a privately-owned or leased telephone switching system, referred to below as a private branch exchange or PBX.
A conventional PBX has standard service functions that are built in when the PBX equipment is manufactured, and optional service functions that can be added by loading additional software modules into the PBX. When the PBX owner orders additional optional service functions, a representative of the PBX vendor brings to the owner's site one or more data media on which copies of the required software modules are stored. The data media are read by a device such as a disk drive in the PBX and stored in a non-volatile memory in the PBX, thereby installing the software in the PBX; then the data media are removed and the owner is billed for the additional service functions.
This method of providing optional service functions is slow and inefficient because it requires a separate visit to the PBX owner's site each time optional service functions are added. To add optional service functions to ten different PBX systems, for example, the vendor's representative must visit ten different sites, which may involve considerable travel time and expense.
A further disadvantage of the conventional method of providing optional service functions is that it invites mistakes, such as installing the wrong optional service functions by inserting the wrong data media into the disk drive in the PBX. Such mistakes can moreover be made intentionally, to provide service functions in a way that deprives the PBX vendor of revenues. This unscrupulous practice has been difficult to control, because once a software module is installed in the PBX, there has been no way to tell whether the module was rightfully or wrongfully installed.
An even greater disadvantage of the conventional method is that the data media containing the software modules can be copied using commercially available equipment. Once a copy is made, further copies can be made from the copy, and these copies can be used to provide pirated service functions to an unlimited number of PBX owners. If such copied media come into general circulation, the PBX vendor faces a serious loss of revenue.